1. Field of the Invention
This invention relates to a novel bioactive substance which suppresses differentiation of undifferentiated cells.
2. Description of the Related Art
Human blood and lymph contain various types of cells and each cell plays important roles. For example, the erythrocyte carries oxygen; platelets have hemostatic action; and lymphocytes prevent infection. These various cells originate from hematopoietic stem cells in the bone marrow. Recently, it has been clarified that the hematopoietic stem cells are differentiated to various blood cells, osteoclasts and mast cells by stimulation of various cytokines in vivo and environmental factors. In the cytokines, there have been found, for example, erythropoietin (EPO) for differentiation to erythrocytes; granulocyte colony stimulating factor (G-CSF) for differentiation to leukocytes; and platelet growth factor (mpl ligand) for differentiation to megakaryocytes which are a platelet producing cells, and the former two have already been clinically applied.
The undifferentiated blood cells are generally classified into two groups consisting of blood precursor cells which are destined to differentiate to specific blood series and hematopoietic stem cells which have differentiation ability to all series and self-replication activity. The blood precursor cells can be identified by various colony assays, however identification method for the hematopoietic stem cells have not been established. In these cells, stem cell factor (SCF), interleukin-3 (IL-3), granulocyte-macrophage colony stimulating factor (GMf-CSF), interleukin-6 (IL-6), interleukin-1 (IL-1), granulocyte colony stimulating factor (G-CSF) and oncostatin M have been reported to stimulate cell differentiation and proliferation. Trials for expansion of hematopoietic stem cells in vitro have been examined in order to replace bone marrow transplantation for applying hematopoietic stem cell transplantation therapy or gene therapy. However, when the hematopoietic stem cells are cultured in the presence of the above mentioned cytokines, multi-differentiation activities and self-replication activities, which are originally in the position of the hematopoietic stem cells, gradually disappeared and are changed to the blood cell precursors which are only to differentiate to specific series after 5 weeks of cultivation, and multi-differentiation activity which is one of the specific features of the hematopoietic stem cells, is lost (Wagner et al. Blood 86, 512-523, 1995).
For proliferation of the blood precursor cells, a single cytokine is not sufficient, but the synergistic action of several cytokines are important. Consequently, in order to proliferate the hematopoietic stem cells while maintaining specific features of the hematopoietic stem cells, it is necessary to add cytokines which suppress differentiation together with the cytokines which proliferate and differentiate the undifferentiated blood cells. In general, many cytokines which stimulate proliferation or differentiation of cells are known, but small numbers of cytokines which suppressed cell differentiation are known. For example, leukemia inhibitory factor (LIF) has an action of proliferation of mouse embryonic stem cells without differentiation, but it has no action against the hematopoietic stem cells or blood precursor cells. Transforming growth factor (TGF-xcex2) has suppressive action for proliferation against various cells, but no fixed actions against the hematopoietic stem cells or blood precursor cells.
Not only blood cells but also undifferentiated cells, especially stem cells are thought to be involved in tissue regeneration. These regeneration of tissues and poliferation of undifferentiated cells in each tissue can be applied in various ways by referring to the known reference (Katsutoshi Yoshizato, Regenerationxe2x80x94a mechanism of regeneration, 1996, Yodosha Pub1. Co.).
Notch is a receptor type membrane protein which is involved in regulation of nerve cells differentiation found in Drosophia. Homologues of the Notch are found in various animal kinds exceeding to the invertebrate and vertebrate including nematoda (Lin-12). Xenopus laevis (Xotch), mouse (Motch) or human (TAN-1). Ligand of the Notch in Drosophila are known. These are Drosophila Delta (Delta) and Drosophila Serrate (Serrate). Notch ligand homologues are found in various animal kinds as similar to the Notch of receptors (Artavanis-Tsakonas et al., Science 268, 225-232, 1995).
Human Notch homologue, TAN-1 is found widely in the tissues in vivo (Ellisen et al., Cell 66, 649-661, 1991). Two Notch analogous molecules other than TAN-1 are reported (Artavanis-Tsakonas et al., Science 268, 225-232, 1995). Expression of TAN-1 was also observed in CD34 positive cells in blood cells by PCR (Polymerase Chain Reaction) (Milner et al., Blood 83, 2057-2062, 1994). However, in relation to humans, gene cloning of human Delta and human Serrate, which are thought to be the Notch ligand, have not been reported.
In Drosophila Notch, binding with the ligand was studied and investigated in detail, and it was found that the Notch can be bound to the ligand with Ca++ at the binding region, which is a repeated amino acid sequence No. 11 and No. 12 in the amino acid sequence repeat of Epidemal Growth Factor (EGF) like repeating (Fehon et al., Cell 61, 523-534, 1990, Rebay et al., ibid. 67, 687-699, 1991 and Japan. Patent PCT Unexam. Pub1. 7-503123). EGF-like repeated sequences are conserved in Notch homologues of the other species. Consequently, the same mechanism in binding with ligand is estimated. An amino acid sequence which is called DSL (Delta-Serrate-Lag-2) near the amino acid terminal, and EGF-like repeated sequence as like in the receptor are conserved in the ligand (Artavanis-Tsakonas et al., Science 268, 225-232, 1995).
The sequence of DSL domain is not found except for the Notch ligand molecules, and is specific to Notch ligand molecule. A common sequence of DSL domain is shown in the sequence listing, SEQ ID NO: 1 in general formula, and comparison with human Delta-1 and human Serrate-1 of the present invention and known Notch ligand molecules are shown in FIG. 1.
EGF-like sequence has been found in thrombomodulin (Jackman et al., Proc. Natl. Acad. Sci. USA 83, 8834-8838, 1986), low density lipoprotein (LDL) receptor (Russell et al., Cell 37, 577-585, 1984), and blood coagulating factor (Furie et al., Cell 53, 505-518, 1988), and is thought to play important roles in extracellular coagulation and adhesion.
Recently, the vertebrate homologues of the cloned Drosophila Delta were found in chicken (C-Delta-1) and Xenopus laevis (X-Delta-1), and it was reported that X-Delta-1 had acted through Xotch in the generation of the protoneuron (Henrique et al., Nature 375, 787-790, 1995 and Chitnis et al., ibid. 375, 761-766,1995). Vertebrate homologue of Drosophila Serrate was found in rat as rat Jagged (Jagged)(Lindsell et al., Cell 80, 909-917, 1995). According to the Lindsell et al., mRNA of the rat Jagged is detected in the spinal cord of fetal rats. As a result of cocultivation of a myoblast cell line that is forced excess expressed rat Notch with a rat Jagged expression cell line, suppression of differentiation of the myoblast cell line is found. However, the rat Jagged has no action against the myoblast cell line without forced expression of the rat Notch.
Considering the above reports, the Notch and ligand thereto may be involved in the differentiation regulation of the nerve cells however, except for some myoblast cells, their actions against cells including blood cells, especially primary cells, are unknown.
In the Notch ligand molecule, from the viewpoint of the prior studies on Drosophila and nematodae,the Notch ligand has specifically a structure of DSL domain which is not found other than in the Notch ligand. Consequently, the fact of having DSL domain means equivalent to ligand molecule for the Notch receptor.
As mentioned above, concerning undifferentiated cells, proliferation that maintains their specificities has not been achieved. Major reasons are that factors suppressing differentiation of the undifferentiated cells are not sufficiently known. An object of the present invention is to provide a compound originated from novel factors which can suppress differentiation of the undifferentiated cells.
We have set up a hypothesis that the Notch and its ligand have action of differential regulation not only for neuroblasts and myoblasts but also for various undifferentiated cells, especially blood undifferentiated cells. However, in case of clinical application in the humans, prior known different species such as chicken or Xenopus laevos type notch ligand have problems of species specificities and antigenicities. Consesquently, to obtain previously unknown human Notch ligand is essentially required. We had an idea that a molecule having DSL domain and EGF-like domain which are common to Notch ligand molecules and a ligand of the human Notch (TAN-1 etc.), which is a human Delta homologue (hereinafter designated as human Delta) and human Serrate homologue (hereinafter designated as human Serrate), may be found. Also we have an idea that these findings may be a candidate for drugs useful for differential regulation of the undifferentiated cells. And we have tried to find out the same.
In order to find out human Notch ligands, we have analyzed amino acid sequences which are conserved in animals other than humans, and tried to find out genes by PCR using mixed primers of the corresponding DNA sequence. As a result of extensive studies, we have succeeded in isolation of cDNAs coding amino acid sequences of two new molecules, novel human Delta-1 and novel human Serrate-1, and have prepared the expression systems of protein having various forms using these cDNAs. Also we have established purification method of the proteins which were purified and isolated.
Amino acid sequences of novel human Delta-1 are shown in the sequence listings, SEQ ID NO: 2-4. DNA sequence coding these sequence is shown in the sequence listing, SEQ ID NO: 8. Amino acid sequence of novel human Serrate-1 is shown in the sequence listings, SEQ ID NO: 5-7. DNA sequence coding these sequence is shown in the sequence listing, SEQ ID NO: 10.
Physiological actions of the these prepared proteins were searched by using nerve undifferentiated cells, preadipocytes, hepatocytes, myoblasts, skin undifferentiated cells, blood undifferentiated cells and immuno undifferentiated cells. As a result, we have found that novel human Delta-1 and novel human Serrate-1 had an action of differentiation-suppressive action to primary blood undifferentiated cells, and had a physiological action to maintain undifferentiated state.
Such actions to the blood undifferentiated cells have never been reported previously, and is a new discovery. No significant toxic actions were noted in the toxicity studies on mice, and useful pharmaceutical effects were suggested. Consequently, the pharmaceutical preparations containing the molecule of the present invention, medium containing the molecule of the present invention, and the device having immobilized thereon the molecule of the present invention are novel drugs and medical materials which can maintain the blood undifferentiated cells in the undifferentiated condition. Antibodies against human Delta-1 and human Serrate-1 are prepared by using antigens of the said human Delta-1 and human Serrate-1, and purification method of the said antibodies are established. The present invention has been completed accordingly.
The present invention further relates to a polypeptide comprising amino acid sequence of SEQ ID NO: 1 of the sequence listing encoded in a gene of human origin, a polypeptide comprising at least amino acid sequence of SEQ ID NO: 2 or NO: 5 of the sequence listing, the polypeptide comprising amino acid sequence of SEQ ID NO: 3 of the sequence listing, the polypeptide comprising amino acid sequence of SEQ ID NO: 4 of the sequence listing, the polypeptide comprising amino acid sequence of SEQ ID NO: 6 of the sequence listing, the polypeptide comprising amino acid sequence of SEQ ID NO: 7 of the sequence listing, the polypeptide having differentiation suppressive action against undifferentiated cells, the polypeptide in which undifferentiated cells are undifferentiated cells other than those of the brain and nervous system or muscular system cells, and the polypeptide in which undifferentiated cells are the undifferentiated blood cells. The present invention also relates to a pharmaceutical composition containing the polypeptides, and the pharmaceutical composition in which use thereof is as a hematopoietic activator. The present invention further relates to a cell culture medium containing the polypeptides, and the cell culture medium in which the cell is the undifferentiated blood cell. The present invention still further relates to a DNA coding a polypeptide at least having amino acid sequence of SEQ ID NO: 2 or NO: 5 of the sequence listing, the DNA having DNA sequence 242-841 of SEQ ID NO: 8 or DNA sequence 502-1095 of SEQ ID NO: 10 of the sequence listing, the DNA coding the polypeptide having amino acid sequence of SEQ ID NO: 3 of the sequence listing, the DNA having DNA sequence 242-1801 of SEQ ID NO: 8 of the sequence listing, the DNA coding the polypeptide having amino acid sequence of SEQ ID NO: 4 of the seqeuence listing, the DNA having DNA sequence 242-2347 of SEQ ID NO: 8of the sequence listing, the DNA coding the polypeptide having amino acid sequence of SEQ ID NO: 6 of the seqeuence listing,the DNA having DNA sequence 502-3609 of SEQ ID NO: 10 of the sequence listing, the DNA coding the polypeptide having amino acid sequence of SEQ ID NO: 7 of the seqeuence listing, and the DNA having DNA sequence 502-4062 of SEQ ID NO: 10 of the sequence listing. The present invention still further relates to a recombinant DNA made by ligating a DNA selected from the groups of DNA hereinabove and a vector DNA which can express in the host cell, a cell transformed by the recombinant DNA, and a process for production of polypeptide by culturing cells and isolating the thus produced compound. The present invention still further relates to an antibody specifically recognizing the polypeptide having the amino acid sequence of SEQ ID NO: 4 of the sequence listing, and an antibody specifically recognizing the polypeptide having the amino acid sequence of SEQ ID NO: 7 of the sequence listing.
The present invention is explained in details in the following.
Preparation of cDNA necessary for gene manipulation, expression analysis by Northern blotting, screening by hybridization, preparation of recombinant DNA, determination of DNA base sequence and preparation of cDNA library, all of which are series of molecular biological experiments, can be performed according to a description of the conventional textbook for the experiments. The above conventional textbook of the experiments is, for example, Maniatis et al. ed. Molecular Cloning, A laboratory manual, 1989, Eds., Sambrook, J., Fritsch, E. F. and Maniatis, T., Cold Spring Harbor Laboratory Press.
A polypeptide of the present invention has at least one of the polypeptides in the sequence listing SEQ ID NO: 1-7. A mutant and allele which naturally occur in the nature are included in the polypeptide of the present invention unless the polypeptides of the sequence listing, SEQ ID NO: 1-7 lose their properties. Modification and substitution of amino acids are described in details in the patent application by the name of Benntt et al. (National Unexam. Pub1. WO96/2645) and can be prepared according to the description thereof.
A DNA sequence coding polypeptides of the sequence listing, SEQ ID NO: 2-4 is shown in the sequence listing, SEQ ID NO: 8, and a DNA sequence coding polypeptides of the sequence listing, SEQ ID NO: 5-7 is show in the sequence listing, SEQ ID NO: 10, together with their amino acid sequences. In these DNA sequences, even if amino acid level mutation is not generated, naturally isolated chromosomal DNA or cDNA thereof may have a possibility to mutate in the DNA base sequence as a result of degeneracy of genetic code without changing amino acid sequence coded by the DNA. A 5xe2x80x2-untranslated region and 3xe2x80x2-untranslated region are not involved in amino acid sequence determination of the polypeptide, so DNA sequences of these regions are easily mutated. The base sequence obtained by these degeneracies of genetic codes is included in the DNA of the present invention.
Undifferentiated cells in the present invention are defined as cells which can grow by specific stimulation, and cells which can be differentiated to the cells having specific functions as a result of the specific stimulations. These include undifferentiated cells of the skin tissues, undifferentiated cells of the brain and nervous systems, undifferentiated cells of the muscular systems and undifferentiated cells of the blood cells. These cells include the cells of self-replication activity which are called stem cells, and the cells having an ability to generate the cells of these lines. The differentiation-suppressive action means suppressive action for autonomous or heteronomous differentiation of the undifferentiated cells, and is an action for maintaining undifferentiated condition. The brain and nervous undifferentiated cells can be defined as cells having ability to differentiate to the cells of the brain or nerve having specific functions by specific stimulation. The undifferentiated cells of the muscular systems can be defined as cells having ability to differentiate to the muscular cells having specific functions by specific stimulation. The blood undifferentiated cells in the present invention can be defined as cell groups consisting of the blood precursor cells which are differentiated to the specific blood series identified by blood colony assay, and hematopoietic stem cells having differentiation to every series and self-replication activities.
In the sequence listing, amino acid sequence in SEQ ID NO: 1 shows general formula of common amino acid sequence of DSL domain which is a common domain structure of the Notch ligand molecules, and at least this domain structure corresponds to the sequence listing, amino acids 158-200 of the human Delta-1, or the sequence listing, amino acids 156-198 of the human Serrate-1.
The amino acid sequence in the sequence listing, SEQ ID NO: 2 is a sequence of the active center of the present invention of human Delta-1 minus the signal peptide, i.e. amino acid sequence from the amino terminal to DSL domain, and corresponds to an amino acid No. 1 to 200 in SEQ ID NO: 4 of the mature full length amino acid sequence of human Delta-1 of the present invention. The amino acid sequence in SEQ ID NO: 3 is amino acid sequence of extracellular domain of the present invention of human Delta-1 deleted the signal peptide, and corresponds to an amino acid No. 1 to 520 in SEQ ID NO: 4 of the mature full length amino acid sequence of human Delta-1 of the present invention. The amino acid sequence of SEQ ID NO: 4 is the mature full length amino acid sequence of the human Delta-1 of the present invention.
The amino acid sequence in the sequence listing, SEQ ID NO: 5 is a sequence of the active center of the present invention of human Serrate-1 minus the signal peptide, i.e. amino acid sequence from the amino terminal to DSL domain, and corresponds to an amino acid No. 1 to 198 in SEQ ID NO: 7 of the mature full length amino acid sequence of human Serrate-1 of the present invention. The amino acid sequence in SEQ ID NO: 6 is amino acid sequence of extracellular domain of the present invention of human Serrate-1 minus the signal peptide, and corresponds to an amino acid No. 1 to 1036 in SEQ ID NO: 7 of the mature full length amino acid sequence of human Serrate-1 of the present invention. The amino acid sequence of SEQ ID NO: 7 is the mature full length amino acid sequence of the human Serrate-1 of the present invention.
The sequence of SEQ ID NO: 8 is a total amino acid sequence of human Delta-1 of the present invention and cDNA coding the same, and the sequence of SEQ ID NO: 10 is total amino acid sequence of human Serrate-1 of the present invention and cDNA coding the same.
The left and right ends of the amino acid sequences in the sequence listings indicate amino terminal (hereinafter designated as N-terminal) and carboxyl terminal (hereinafter designated as C-terminal), respectively, and the left and right ends of the nucleotide sequences are 5xe2x80x2-terminal and 3xe2x80x2-terminal, respectively.
Cloning of human Notch ligand gene can be performed by the following method. During the evolution of the organisms, a part of amino acids sequences of the human Notch ligand is conserved. DNA sequence corresponding to the conserved amino acid sequence is designed, and is used as a primer of RT-PCR (Reverse Transcription Polymerase Chain Reaction), then a PCR template of the human origin is amplified by PCR reaction, thereby fragments of human Notch ligand can be obtainable. Furthermore, RT-PCR primer is prepared by applying the known DNA sequence information of the Notch ligand homologue of the organisms other than humans, and the known gene fragments can be possibly obtained from PCR template of the said organisms.
In order to perform PCR for obtaining fragments of human Notch ligand, PCR for DSL sequence is considered, but a large number of combinations of DNA sequence corresponding to amino acid sequence conserved in this region can be expected, and a design for PCR is difficult. As a result, PCR of the EGF-like sequence has to be selected. As explained hereinbefore,since EGF-like sequence is conserved in a large number of molecules, to obtain the fragments and identification are extremely difficult.
We have designed and prepared about 50 PCR primer sets, for example the primer set of the sequence shown in Example 1, PCR was performed with these primer sets by using PCR template of cDNA prepared from poly A+ RNA of various tissues of human origin, and more than 10 PCR products from each tissue were subcloned, as well as performing sequencing for more than 500 types. A clone having a desired sequence could be identified. Namely, the obtained PCR product is cloned in the cloning vector, transforming the host cells by using recombinant plasmid which contains the PCR product, culturing the host cells containing the recombinant plasmid on a large scale, purifying and isolating the recombinant plasmid, checking the DNA sequence of PCR product which is inserted into the cloning vector, and trying to obtain the gene fragment which may have a sequence of human Delta-1 by comparing with the sequence of the known Delta of other species. We have succeeded to find out the gene fragment which contains a part of cDNA of human Delta-1, the same sequence of DNA sequence from 1012 to 1375 described in the sequence listing, SEQ ID NO: 8.
We have also designed and prepared about 50 PCR primer sets, for example the primer set of the sequence shown in Example 3, and PCR was performed with these primer sets by using PCR template of cDNA prepared from poly A+ RNA of various tissues of human origin, and more than 10 PCR products from each tissue were subcloned, as well as performing sequencing for more than 500 types. A clone having a desired sequence could be identified. Namely, the obtained PCR product is cloned in the cloning vector, transforming the host cells by using recombinant plasmid which contains the PCR product, culturing the host cells containing the recombinant plasmid on a large scale, purifying and isolating the recombinant plasmid, checking the DNA sequence of PCR product which is inserted into the cloning vector, and trying to obtain the gene fragment which may have a sequence of human Serrate-1 by comparing with the sequence of the known Serrate of other species. We have succeeded to find out the gene fragment which contains a part of cDNA of human Serrate-1, the same sequence of DNA sequence from 1272 to 1737 described in the sequence listing, SEQ ID NO: 10.
A full length of the objective gene can be obtained from the human genomic gene library or cDNA library by using the thus obtained human Delta-1 fragment or human Serrate-1 gene fragment. The full length cloning can be made by isotope labelling and non-isotope labelling with the partial cloning gene, and screening the library by hybridization or other method. Isotope labelling can be performed by, for example, terminal labelling by using [32P] xcex3-ATP and T4 polynucleotide kinase, or other labelling methods such as nick translation or primer extension method can be applied. In another method, human originated cDNA library is ligated into the expression vector, expressing by COS-7 or other cells, and screening the objective gene by expression cloning to isolate cDNA of the ligand. In the expression cloning, a cell sorter fractionation method which is applied with binding with polypeptide containing amino acid sequence of prior known 4 Notches such as TAN-1, and a detection method by film emulsion using radioisotope can be mentioned. In this specification, methods for obtaining genes of human Delta-1 and human Serrate-1 are explained, and in addition to that obtaining the Notch ligand homologue gene of the other organism is important for analysis of ligand action. This may be made by the same treatment. The obtained gene is subjected to DNA sequence determination and amino acid sequence can be estimated.
As shown in Example 2, gene fragments containing human Delta-1 PCR product are labelled with radioisotope to prepare hybridization probe, screening is preformed using cDNA of human placenta origin as the screening library, DNA sequences of the thus obtained clones, are determined, and the clone is obtained DNA nucleotide sequence shown in the sequence listing, SEQ ID NO: 8, and shown to name the amino acid sequence coded in the sequence listing, SEQ ID NO: 4. We have succeeded in cloning cDNA coding full length of amino acids sequence of human Delta-1.
These sequences were compared with the data base (Genbank release 89, June, 1995), and found that these were novel sequences. The said amino acid sequence was analyzed in hydrophilic part and hydrophobic part according to a method by Kyte-Doolittle (J. Mol. Biol. 157: 105, 1982). A result indicated that human Delta-1 of the present invention is expressed on cells as a cellular membrane protein having a transmembrane domain.
As shown in Example 4, gene fragments containing human Serrate-1 PCR product are labelled with radioisotope to prepare hybridization probe, screening is preformed using cDNA of human placenta origin as the screening library, DNA sequences of the thus obtained clones are determined, and the clone is obtained containing DNA nucleotide sequence shown in the sequence listing, SEQ ID NO: 10, and shown to have the amino acid sequence coded in the sequence listing, SEQ ID NO: 7. In this screening, an intracellular part of gene sequence coding a full length of amino acids sequence, namely a peripheral part of termination codon can not be cloned. Consequently, as shown in Example 4, gene cloning is performed by RACE method (rapid amplification of cDNA ends, Frohman et al., Proc. Natl. Acad. Sci. U.S.A. 85, 8998-9002, 1988) and finally succeeded in cloning of cDNA coding full length of amino acid sequence of human Serrate-1.
These sequences were compared with the data base (Genbank release 89, June, 1995), and found that these were novel sequences. The said amino acid sequence was analyzed in hydrophilic part and hydrophobic part according to a method by Kyte-Doolittle (J. Mol. Biol. 157: 105, 1982). A result indicated that human Serrate-1 of the present invention is expressed on cells as a cellular membrane protein having a transmembrane domain.
Examples of plasmids integrated with cDNA are, for example, E. coli originated pBR322, pUC18, pUC19, pUC118 and pUC119 (Takara Shuzo Co. Japan), but other plasmids can be used if they can replicate and proliferate in the host cells. Examples of phage vectors integrated with cDNA are, for example, xcexgt10 and xcexgt11, but other vectors can be used if they can grow in the host cells. The thus obtained plasmids are transduced into suitable host cells such as genus Escherichia and genus Bacillus using calcium chloride method. Examples of the above genus Escherichia are Eseherichia coli K12HB101, MC1061, LE392 and JM109. Example of the above genus Bacillus is Bacillus subtilis MI114. Phage vector can be introduced into the proliferated E. coli by the in vitro packaging method (Enquist and Sternberg Meth. Enzymd., 68, 281-1979).
According to the analysis of amino acid sequence of the human Delta-1, amino acid sequence of a precursor of human Delta-1 consists of 723 amino acids residue shown in the sequence listing, SEQ ID NO: 8, and the signal peptide domain is estimated to correspond to an amino acid sequence of 21 amino acids residue from No.xe2x88x9221 methionine to No. xe2x88x921 serine of the sequence listing; extracellular domain: 520 amino acids residue from No. 1 serine to No. 520 glycine; transmembrane domain: 32 amino acids residue from No. 521 proline to No. 552 leucine; and intracellular domain: 150 amino acids region from No. 553 glutamine to No. 702 valine. These domains are estimated domain construction from amino acid sequences, and actual presence form may differ from the above structure, and constitutional amino acids of each domain hereinabove defined may have possibility to change 5 to 10 amino acids sequence.
According to a comparison in amino acid sequence of human Delta-1 and Delta homologue of the other organisms, the homologies with Drosophila Delta, chicken Delta and Xenopus laevis are 47.6%, 83.3% and 76.2%, respectively. The human Delta-1 of the present invention is different from these Deltas and is novel substance which is clarified at first by the present inventors. Search from all of organisms in the above data base indicated that polypeptides having the identical sequence of the human Delta-1 could not be found.
The homologues of Notch ligand have evolutionally conserved common sequence, i.e. repeated DSL sequence and EGF-like sequence. As a result of comparison with amino acid sequence of human Delta-1, these conserved sequence is estimated. Namely, DSL sequence corresponds to 43 amino acids residue from No. 158 cysteine to No. 200 cysteine of the amino acid sequence in the sequence listing, SEQ ID NO: 4. EGF-like sequence exists with 8 repeats wherein, in the amino acid sequence in the sequence listing, SEQ ID NO: 4, the first EGF-like sequence from No. 205 cysteine to No. 233 cysteine; the second EGF-like sequence from No. 236 cysteine to No. 264 cysteine; the third EGF-like sequence from No. 271 cysteine to No. 304 cysteine; the fourth EGF-like sequence from No. 311 cysteine to No. 342 cysteine; the fifth EGF-like sequence from No. 349 cysteine to No. 381 cysteine; the sixth EGF-like sequence from No. 388 cysteine to No. 419 cysteine; the seventh EGF-like sequence from No. 426 cysteine to No. 457 cysteine; and the eighth EGF-like sequence from No. 464 cysteine to No. 495 cysteine.
A part of sugar chain attached is estimated from amino acid sequence of the human Delta-1 may be No. 456 asparagine residue in the sequence listing, SEQ ID NO: 4 as a possible binding site of N-glycoside bonding for N-acetyl-D-glucosamine. O-glycoside bond of N-acetyl-D-galactosamine is estimated to be a serine or threonine residue rich part. Protein bound with sugar chain is generally thought to be stable in vivo and to have strong physiological activity. Consequently, in the amino acid sequence of polypeptide having sequence of the sequence listing, SEQ ID NO: 2, 3 or 4, polypeptides having N-glucoside or O-glucoside bond with sugar chain of N-acetyl-D-glucosamine or N-acetyl-D-galactosamine is included in the present invention.
According to the analysis of amino acid sequence of the human Serrate-1, amino acid sequence of a precursor of human Serrate-1 consists of 1218 amino acids residue shown in the sequence listing, SEQ ID NO: 10, and the signal peptide domain is estimated to correspond 31 amino acids residue in the amino acid sequence from No. xe2x88x9231 methionine to No. xe2x88x921 alanine of the sequence listing; extracellular domain: 1036 amino acids residue from No. 1 serine to No. 1036 asparagine; transmembrane domain: 26 amino acids residue from No. 1037 phenylalanine to No. 1062 leucine; and intracellular domain: 106 amino acids domain from No. 1063 arginine to No. 1187 valine. These domains are estimated domain construction from amino acid sequences, and actual presence form may differ from the above structure, and constitutional amino acids of each domain hereinabove defined may have possibility to change 5 to 10 amino acids sequence.
According to a comparison in amino acid sequence of human Serrate-1 and Serrate homologue of the other organisms, the homologies with Drosophila Serrate, and rat Jagged are 32.1% and 95.3%, respectively. The human Serrate-1 of the present invention is different from these Serrates and is novel substance which is clarified at first by the present inventors. Search from all of organisms in the above data base indicated that polypeptides having the identical sequence of the human Serrate-1 could not find out.
The homologues of Notch ligand have evolutionally conserved common sequence, i.e. repeated DSL sequence and EGF-like sequence. As a result of comparison with amino acid sequence of human Serrate-1 and other Notch ligand homologues, these conserved sequence is estimated. Namely, DSL sequence corresponds to 43 amino acids residue from No. 156 cysteine to No. 198 cysteine of the amino acid sequence in the sequence listing, SEQ ID NO: 7. EGF-like sequence exists with 16 repeats wherein, in the amino acid sequence in the sequence listing, SEQ ID NO: 7, the first EGF-like sequence from No. 205 cysteine to No. 231 cysteine; the second EGF-like sequence from No. 234 cysteine to No. 262 cysteine; the third EGF-like sequence from No. 269 cysteine to No. 302 cysteine; the fourth EGF-like sequence from No. 309 cysteine to No. 340 cysteine; the fifth EGF-like sequence from No. 346 cysteine to No. 378 cysteine; the sixth EGF-like sequence from No. 385 cysteine to No. 416 cysteine; the seventh EGF-like sequence from No. 423 cysteine to No. 453 cysteine; the eighth EGF-like sequence from No. 462 cysteine to No. 453 cysteine; the nineth EGF-like sequence from No. 498 cysteine to No. 529 cysteine; the 10th EGF-like sequence from No. 536 cysteine to No. 595 cysteine; the 11th EGF-like sequence from No. 602 cysteine to No. 633 cysteine; the 12th EGF-like sequence from No. 640 cysteine to No. 671 cysteine; the 13th EGF-like sequence from No. 678 cysteine to No. 709 cysteine; the 14th EGF-like Sequence from No. 717 cysteine to No. 748 cysteine; the 15th EGF-like sequence from No. 755 cysteine to No. 786 cysteine; and the 16th EGF-like sequence from No. 793 cysteine to No. 824 cysteine. However,the 10th EGF-like sequence has irregular sequence containing 10 residues of cysteine.
A part of sugar chain attached is estimated from amino acid Sequence of the human Serrate-1 may be No. 112, 131, 186, 351, 528, 554, 714, 1014 and 1033 asparagine residue in the sequence listing, SEQ ID NO: 7 as a possible binding site of N-glycoside bonding for N-acetyl-D-glycosamine. O-glycoside bond of N-acetyl-D-galactosamine is estimated to be a serine or threonine residue rich part. Protein bound with sugar chain is generally thought to be stable in vivo and to have strong physiological activity. Consequently,in the amino acid sequence of polypeptide having sequence of the sequence listing, SEQ ID NO: 5, 6 or 7, polypeptides having N-glucoside or O-glucoside bond with sugar chain of N-acetyl-D-glucosamine or N-acetyl-D-galactosamine is included in the present invention.
As a result of studies on binding of Drosophila Notch and its ligand, amino acid region necessary for binding with ligand of Drosophila Notch with the Notch is from N-terminal to DSL sequence of the mature protein, in which signal peptide is removed (Japan. Pat. PCT Unexam. Pub1. No. 7-503121). This fact indicates that a domain necessary for expression of ligand action of human Notch ligand molecule is at least the DSL domain, i.e. a domain containing amino acid sequence of the sequence listing, SEQ ID NO: 1, and a domain at least necessary for expression of ligand action of human Delta-1 is novel amino acid sequence shown in the sequence listing, SEQ ID NO: 2, and further a domain at least necessary for expression of ligand action of human Serrate-1 is novel amino acid sequence shown in the sequence listing, SEQ ID NO: 5.
An mRNA of human Delta-1 can be detected by using DNA coding a part or all of gene sequence in the sequence listing, SEQ ID NO: 8, and an mRNA of human Serrate-1 can be detected by using DNA coding a part or all of gene sequence in the sequence listing, SEQ ID NO: 10. For example, a method for detection of expression of these genes can be achieved by applying with hybridization or PCR by using complementary nucleic acids of above 12 mer or above 16 mer, preferably above 18 mer having nucleic acid sequence of a part of sequence in the sequence listing, SEQ ID NO: 8 or 10, i.e. antisense DNA or antisense RNA, its methylated, methylphosphated. deaminated, or thiophosphated derivatives. By the same method, detection of homologues of the gene of other organisms such as mice or gene cloning can be achieved. Further cloning of genes in the genome including humans can be made. Using these genes cloned by such like methods, further detailed functions of the human Delta-1 or human Serrate-1 of the present invention can be clarified. For example, using the modern gene manipuration techniques, every methods including transgenic mouse, gene targeting mouse or double knockout mouse in which genes relating to the gene of the present invention are inactivated, can be applied. If abnomalities in the genome of the present gene is found, application to gene diagnosis and gene therapy can be made.
A transformant in which vector pUCDL-1F, which contains cDNA coding total amino acid sequence of human Delta-1 of the present invention, is transformed into E. coli JM109, has been deposited in the National Institute of Bioscience and Human-Technology, Agency of Industrial Science and Technology, MITI, of 1-1-3, Higasi, Tsukuba-shi, Ibaragi-ken, Japan, as E. coli: JM109-pUCDL-1F. Date of deposit was Oct. 28, 1996, and deposition No. is FBRM BP-5728. A transformant in which vector pUCSR-1, which contains cDNA coding total amino acid sequence of human Serrate-1 of the present invention, is transformed into E. coli JM109, has been deposited in the National Institute of Bioscience and Human-Technology, Agency of industrial Science and Technology, MITI, of 1-1-3, Higasi, Tsukuba-shi, Ibaragi-ken, Japan, as E. coli: JM109-pUCSR-1. Date of deposit was October 28, 1996, and deposition No. is FBRPM BP-5726.
Exprssion and purification of various forms of human Delta-1 and human Serrate-1 using cDNA coding amino acid sequence of human Delta-1 and human Serrate-1 isolated by the above methods are known in the references (Kriegler, Gene Transfer and Expression- A Laboratory Manual Stockton Press, 1990 and Yokota et al. Biomanual Series 4, Gene transfer and expression and analysis, Yodosha Co., 1994). A cDNA coding the amino acid sequence of the isolated said human Delta-1 and human Serrate-1 is ligated to preferable expression vector and is produced in the host cells of eukaryotic cells such as animal cells and insect cells or prokaryotic cells such as bacteria.
In the expression of human-Delta-1 and human Serrate-1 of the present invention, DNA coding polypeptide of the present invention may have the translation initiation codon in 5xe2x80x2-terminal and translation termination codon in 3xe2x80x2-terminal. These translation initiation codon and translation termination codon can be added by using preferable synthetic DNA adapter. Further for expression of the said DNA, promoter is linkaged in the upstream of the DNA sequence. Examples of vector are plasmid originated from Bacillus, plasmid originated from yeast or bacteriophage such as xcex-phage and animal virus such as retrovirus and vaccinia virus.
Examples of promoters used in the present invention are any promoters preferable for corresponding to the host cells used in gene expression.
In case that the host cell in the transformation is genus Eseherichia, tac-promoter, trp-promoter and lac-promoter are preferable, and in case of host of genus Bacillus, SP01 promoter and SP02 promoter are preferable, and in case of host of yeast, PGK promoter, GAP promoter and ADH promoter are preferable.
In case that the host cell is animal cells, a promoter originated from SV40 such as SRxcex1 promoter as described in Example 5, promoter of retrovirus, metallothionein promoter and heatshock promoter can be applied.
Polypeptide of the present invention can be expressed by using the expression vector having ability to be used by any person skilled in the arts.
Expression of the polypeptide of the present invention can be made by using only DNA coding the amino acid sequence of the sequence listing, SEQ ID NO: 2, 3, 4, 5, 6 or 7. However, the protein added with specific function can be produced by using DNA, to which added cDNA coding the known antigen epitope for easier detection of the produced polypeptide or added cDNA coding the immunoglobulin Fc for forming multimer.
As shown in Example 5, we have prepared expression vectors, which express extracellular proteins of human Delta-1, as follows.
1) DNA coding the amino acids from No. 1 to 520 in amino acid sequence in the sequence listing, SEQ ID NO: 3,
2) DNA coding chimera protein to which added polypeptide having 8 amino acid, i.e. an amino acid sequence consisting of Asp Tyr Lys Asp Asp Asp Asp Lys (hereinafter designates FLAG sequence, the sequence listing, SEQ ID NO: 10), in the C-terminal of the amino acids from No. 1 to 520 in amino acid sequence in the sequence listing, SEQ ID NO: 3, and
3) DNA coding chimera protein to which added Fc sequence below the hinge region of human IgG1 (refer to International Patent Pub1. WO96/11221) in the C-terminal of the amino acids from No. 1 to 520 in amino acid sequence in the sequence listing, SEQ ID NO: 3, and to have dimer structure by disulfide bond in the hinge region,
are ligated individually with the expression vector pMKITNeo (Maruyama et al. Japan Molecular Biology Soc. Meeting Preliminary lecture record, obtainable from Dr. Maruyama in Tokyo Medical and Dental College, containing promoter SRxcex1) to prepare extracellular expression vectors of human Delta-1.
The full-length expression vectors of the human Delta-1 as the expression vectors, which express full-length proteins of the human Delta-1, can be prepared as follows.
4) DNA coding amino acids from No. 1 to 702 in the sequence listing, SEQ ID NO: 4 and
5) DNA coding chimera protein to which added polypeptide having FLAG sequence in the C-terminal of amino acids from No. 1 to 702 in the sequence listing, SEQ ID NO: 4
are ligated individually with the expression vector pMlKITNeo to prepare the full-length expression vectors of human Delta-1. The transformant is prepared by using expression plasmid containing DNA coding the thus constructed said human Delta-1.
As shown in Example 6, we have prepared expression vectors, which express extracellular proteins of human Serrate-1, as follows.
6) DNA coding the amino acids from No. 1 to 1036 in amino acid sequence in the sequence listing, SEQ ID NO: 6,
7) DNA coding chimera protein to which added polypeptide having FLAG sequence in the C-terminal of the amino acids from No. 1 to 1036 in amino acid sequence in the sequence listing, SEQ ID NO: 6, and
8) DNA coding chimera protein to which added said Fc sequence in the C-terminal of the amino acids from No. 1 to 1036 in amino acid sequence in the sequence listing, SEQ ID NO: 6, and to have dimer structure by disulfide bond in the hinge region,
are ligated individually with the expression vector pMKITNeo to prepare extracellular expression vectors of human Serrate-1.
The full-length expression vectors of the human Serrate-1 as the expression vectors,which express full-length proteins of the human Serrate-1, can be prepared as follows.
9) DNA coding amino acids from No. 1 to 1187 in the sequence listing, SEQ ID NO: 7 and
10) DNA coding chimera protein to which added polypeptide having FLAG sequence in the C-terminal of amino acids from No. 1 to 1187 in the sequence listing, SEQ ID NO: 7
are ligated individually with the expression vector pMKITNeo to prepare the full-length expression vectors of human Serrate-1. The transformant is prepared by using expression plasmid containing DNA coding the thus constructed said human Serrate-1.
Examples of the host are genus Escherichia, genus Bacillus, yeast and animal cells. Examples of animal cells are simian cell COS-7 and Vero, Chinese hamster cell CHO and silk worm cell SF9.
As shown in Example 7, the above expression vectors 1)-10) are transduced individually; the human Delta-1 or human Serrate-1 are expressed in COS-7 cell (obtainable from the Institute of Physical and Chemical Research, Cell Development Bank, RCB0539), and the transformants which were transformed by these expression plasmids, can be obtained. Further, human Delta-1 polypeptide and human Serrate-1 polypeptide can be produced by culturing the transformants under preferable culture condition in medium by known culture method.
As shown in Example 8, human Delta-1 polypeptide and human Serrate-1 polypeptide can be isolated and purified from the above cultured mass, in general, by the following methods.
For extraction of the substance from cultured microbial cells or cells, microbial cells or cells are collected by known method such as centrifugation after the cultivation, suspended in preferable buffer solution, disrupted the microbial cells or cells by means of ultrasonication, lysozyme and/or freeze-thawing and collected crude extract by centrifugation or filtration. The buffer solution may contain protein-denaturing agents such as urea and guanidine hydrochloride or surface active agents such as Triton-X. In case of secretion in the cultured solution, the cultured mass is separated by the known method such as centrifugation to separate from microbial cells or cells and the supernatant solution is collected.
The thus obtained human Delta-1 or human Serrate-1, which are contained in the cell extracts or cell supernatants, can be purified by known protein purification methods. During the purification process, for confirmation of existence of the protein, in case of the fused proteins of the above FLAG and human IgGFc, they can be detected by immunoassay using antibody against known antigen epitope and can be purified. In case of not to express as such the fused protein, the antibody in Example 9 can be used for detection.
Antibodies, which specifically recognize human Delta-1 and human Serrate-1, can be prepared as shown in Example 9. Antibodies can be prepared by the methods described in the reference (Antibodies a laboratory manual, E. Harlow et al., Cold Spring Harbor Laboratory) or recombinant antibodies expressed in cells by using immunoglobulin genes isolated by gene cloning method. The thus prepared antibodies can be used for purification of human Delta-1 and human Serrate-1. The human Delta-1 or human Serrate-1 can be detected and assayed by using antibodies which recognize specifically human Delta-1 or human Serrate-1 as shown in Example 9, and can be used for diagnostic agents for diseases accompanied with abnormal differentiation of cells such as malignant tumors.
More useful purification method is the affinity chromatography using antibody. Antibodies used in this case are antibodies described in Example 9. For fused protein, antibodies against FLAG in the case of FLAG, and protein G or protein A in the case of human IgGFc as shown in Example 8.
Any fused protein other than the protein as shown hereinabove can be used. For example, histidine Tag and myc-tag can be mentioned. Any fused proteins can be prepared by using methods of present day genetic engineering techniques other than the known methods, and peptides of the present invention derived from those fused proteins are in the scope of the present invention.
Physiological functions of the thus purified human Delta-1 and human Serrate-1 proteins can be identified by various assay methods, for example, physiological activity assaying methods using cell lines and animals such as mice and rats, assay methods of intracellular signal transduction based on molecular biological means, binding with Notch receptor etc.
We have observed actions for blood undifferentiated cells by using IgG1 chimera proteins of human Delta-1 and human Serrate-1.
As a result, we have found that, as shown in Example 10, in the umbilical cord blood derived blood undifferentiated cells, in which CD34 positive cell fraction is concentrated, polypeptides of the present invention have suppressive action of colony forming action against blood undifferentiated cells, which shows colony formation in the presence of cytokines. The suppressive action is only observed in the presence of SCF. This kind of effect has never been known.
As shown in Example 11, we have found that a maintenance of colony forming cells is significantly extended by addition of IgG1 chimera protein of human Delta-1 or human Serrate-1 in the long term (8 weeks) liquid culture in the presence of cytokines such as SCF, IL-3, IL-6, GM-CSF and Epo. Further we have found that the polypeptides of the present invention had an action not to suppress growth of the colony forming cells. A cytokine, MIP-1 xcex1having migration and differentiation suppressive action of blood cells (Verfaillie et al., J. Exp. Med. 179, 643-649, 1994), has no action for maintaining undifferentiation for blood undifferentiated cells.
Further as shown in Example 12, we have found that as a result of adding IgG1 chimera protein of human Delta-1 or human Serrate-1 to the liquid culture in the presence of cytokines, the human Delta-1 and human Serrate-1 had activities for significantly maintaining LTC-IC (Long-Term Culture-Initiating Cells) number, which is positioned most undifferentiated blood stem cells in the human blood undifferentiated cells.
These results indicate that the human Delta-1 and human Serrate-1 suppress differentiation of blood undifferentiated cells, and these actions spread from blood stem cells to colony forming cells. These physiological actions are essential for in vitro expansion of blood undifferentiated cells. Cells cultured in the medium containing human Delta-1 or human Serrate-1 are efficient in recovery of suppresion of bone marrow after administration of antitumor agents, accordingly in vitro growth of hemopoietic stem cells may be possible if other conditions would be completed. Further pharmaceuticals containing the polypeptide of the present invention have action protection and release of the bone marrow suppressive action, which is observed in adverse effects of antitumor agents.
Suppressive action for differentiation of cells in the undifferentiated cells other than blood cells is expected and stimulating action for tissue regeneration can be expected.
In the pharmaceutical use, polypeptides of the present invention are lyophilized with adding preferable stabilizing agents such as human serum albumin, and is used in dissolved or suspended condition with distilled water for injection when it is in use. For example, preparation for injection or infusion at the concentration of 0.1-1000 xcexcg/ml may be provided. A mixture of the compound of the present invention 1 mg/ml and human serum albumin 1 mg/ml divided in a vial could maintain activity of the said compound for long term. For culturing and activating cells in vitro, lyophilized preparation or liquid preparation of the polypeptide of the present invention are prepared and are added to the medium or immobilized in the vessel for culture. Toxicity of the polypeptide of the present invention was tested. Any polypeptide, 10 mg/kg was administered intraperitoneally in mice, but no death of mice was observed.
In vitro physiological activity of the polypeptide of the present invention can be evaluated by administering to disease model mice or its resembled disease rats or monkeys, and examining recovery of physical and physiological functions and abnormal findings. For example, in case of searching abnormality in relation to hemopoietic cells, bone marrow suppressive model mice are prepared by administering 5-FU series of antitumor agents, and bone marrow cell counts, peripheral blood cell counts and physiological functions are examined in the administered group or the non administered group of mice. Further, in case of searching in vitro cultivation and growth of hemopoietic undifferentiated cells including hemopoietic stem cells, the bone marrow cells of mice are cultured in the groups with or without addition of the compound of the present invention, and the cultured cells are transferred into the lethal dose irradiated mice. Result of recovery is observed with the indications of survival rate and variation of blood counts. These results can be extrapolated to the humans, and accordingly useful effective data for evaluation of the pharmacological activities of the compound of the present invention can be obtained.
Applications of the compound of the present invention for pharmaceuticals include diseases with abnormal differentiation of cells, for example leukemia and malignant tumors. These are cell therapy, which is performed by culturing human derived cells in vitro while maintaining their original functions or adding new functions, and a therapy, which is performed by regenerating without damaging the functions orginally existing of the originally existed in the tissues by administering the compound of the present invention under the regeneration after tissue injury. Amount of administration may differ in the type of preparation and ranges from 10 xcexcg/kg to 10 mg/kg.
Further strong physiological activity can be achieved by expression of forming multimer of the polypeptide of the present invention.
As shown in Example 10, since the suppressive action of human Delta-1 and human Serrate-1 is stronger in the IgG chimera protein having dimer structure, a form of stronger physiological activity is preferably expressed in the form of multimer formation.
Human Delta-1 and human Serrate-1 having multimer structure can be produced by a method of expressing chimera protein with human IgG Fc region as described in the example and expressing the multimer having disulfide bond with hinge region of the antibody, or a method expressing chimera protein, in which antibody recognition region is expressed in the C-terminal or N-terminal, and reacting with the polypeptide containing extracellular part of the thus expressed said human Delta 1 and Human Serrate 1 and the antibody which recognize specifically the antibody recognition region in the C-terminal or N-terminal. In the other methods, a method, in which a fused protein expressed with only the hinge region of the antibody and the dimerized by disulfide bond, can be mentioned. The multimer of human Delta-1 and human Serrate-1 having higher specific activity than the dimer can be obtained. The said multimer is constructed by fused protein which is prepared for expressing the peptide in the C-terminal, N-terminal or other region. The protein is prepared in the form of forming disulfide bond without effecting in any activities of the other human Delta-1 or human Serrate-1. The multimer structure can also be expressed by arranging one or more peptide, which is selected from polypeptides containing amino acids sequence of the sequence listing, SEQ ID NO: 2, 3, 5 or 6, with genetic engineering method in series or in parallel. Other known methods for providing multimer structure having dimer or higher can be applied. Accordingly, the present invention includes any polypeptides containing amino acid sequences described in the sequence listing, SEQ ID NO: 2, 3, 5 or 6 in the form of dimer or higher structure prepared by genetic engineering technique.
Further in the other method, multimerization method using chemical cross-linker can be mentioned. For example, dimethylsuberimidate dihydrochloride for cross-linking lysine residue, N-(xcex3-maleimidebutyryloxy) succinimide for cross-linking thiol group of cysteine residue and glutaraldehyde for cross-linking between amino groups can be mentioned. The multimer with dimer or more can be synthesized by applying these cross-linking reactions. Accordingly, the present invention includes any polypeptides containing amino acid sequences described in the sequence listing, SEQ ID NO: 2, 3, 5 or 6 in the form of dimer or more structure prepared by chemical cross-linking agents.
In application of medical care in which cells are proliferated and activated in vitro and are returned to the body, human Delta-1 or human Serrate-1 of the form hereinabove can be added directly in the medium, but immobilization can also be made. Immobilization method includes applying amino group or carboxyl group in the peptide, using suitable spacers or the above mentioned cross-linkers, and the polypeptide can be covalently bound to the culture vessels. Accordingly, the present invention includes any polypeptides containing amino acid sequences described in the sequence listing, SEQ ID NO: 2, 3, 5 or 6 in the form of existing on the solid surface.
Since the natural human Delta-1 and human Serrate-1 are cell membrane proteins, differentiation suppressive action in Examples can be expressed by cocultivating with cells expressing these molecules and blood undifferentiated cells. Consequently, this invention includes cocultivation method with transformed cells by using DNA coding amino acid sequences in the sequence listing, SEQ ID NO: 2-7 and undifferentiated cells.
Expressed cell may be COS-7 cell as shown in Examples, but cells of human origin are preferable, and further expressed cells may be cell line or any of human in vivo blood cells and somatic cells. Consequently, the polypeptide can be expressed in vivo by integrated into vectors for gene therapy.
As shown in Example 10, FLAG chimera protein of human Delta-1 or human Serrate-1, both of which are low concentrated monomer, shows not a colony formation suppressive action but a colony formation stimulating action. This action may be involved in expressing Notch receptor and Notch ligand in the occasion of cell division of blood undifferentiated cells and acting the polypeptide of the present invention as an antagonist for that action. This suggests that the polypeptide having amino acid sequence of the sequence listing, SEQ ID NO: 1, 2, 4 or 5, shows colony formation stimulation action by controlling the concentration of its action.
This fact suggests that inhibition of binding the polypeptide having amino acid sequence in the sequence listing, SEQ ID NO: 2-7 and these receptors can be used for finding out molecules and compounds for stimulating cell differentiation. The methods include binding experiment using radio isotope, luciferase assay using transcriptional control factors, a down stream molecule of the Notch receptor, and simulation on the computer by X-ray structural analysis. Accordingly, the present invention includes screening method for pharmaceuticals using polypeptide in the sequence listing, SEQ ID NO: 2-7.
As shown in Example 13, specific leukemia cells can be differentiated by using IgG chimera protein of human Delta-1 or human Serrate-1. Consequently, the present invention can be applied for diagnostic reagents for leukemia or isolation of specific blood cells. This result indicates that human Delta-1 or human Serrate-1 molecule binds specifically with its receptor, a Notch receptor molecule. For example, expression of Notch receptor can be detected by using fused protein with the above extracellular region and human IgGFc. Notch is known to involve in some type of leukemia (Ellisen et al., Cell 66, 649-661, 1991). Accordingly, the polypeptide having amino acids sequence in the sequence listing, SEQ ID NO: 2, 3, 5 and 6 can be used for diagnostic reagents for in vitro or in vivo.